While some research supports some positive effects of negative ion exposure, there is no evidence-based medication that supports negative ion therapy. So don't bother getting any household negative ionizers. They can produce hazardous indoor ozone and only waste space and electricity. VOCs are considered indoor pollutants and can cause health problems.
Unfortunately, ionizers are ineffective in reducing VOCs in the air. As more information is disseminated and presented to the public about the dangers of air ionizers, the more informed consumers will be before purchasing an air purifier, and they are likely to be aware of and avoid these potentially hazardous ionizing air systems. Another recent study of air ionizers in school classrooms reduced particle concentrations and led to some improvements in respiratory health among children 11 to 14 years old, ionizers had an adverse effect on heart rate variability (a measure of cardiovascular health), meaning that any benefit to the lungs came at a cost to the heart. Since the conflicting data associated with the ionizer remains persistent, I usually keep my ionizer option turned off.
Laboratory tests were conducted with particulate air and gas samples in a large semi-furnished chamber and in a field test with an ionizing device installed in an air handling unit serving an occupied office building. These ionizers turn on for 8 hours every day, and I have a Therapure TPP300D with UV+ ionizer that turns on for 8 hours in my living room. Air ionizers are designed to help provide cleaner air and they do so through the use of ionized particles. Ionizer air purifiers are generally safe because ionizers aren't energized enough to be harmful to you.
However, to get rid of the dangers of second and third hand smoking from my roommate, I now plan to keep my ionizer turned on only for 30-40 minutes when no one is in the room, and then turn off the ionizer before anyone comes in. Chamber and field tests found that an ionizing device led to a decrease in some volatile organic compounds (VOC), including xylenes, but an increase in others, more prominently oxygenated VOCs (e.g.